Oral Medicine, Oral Radiology and Oral Diagnosis
Oral Medicine, Oral Radiology and Oral Diagnosis
This domain tests vesiculobullous disease, chronic ulceration, orofacial pain and the radiographic patterns that narrow a differential diagnosis.
Core rules
- Recurrent aphthous stomatitis: minor (commonest, heals without scar), major (larger, scarring), herpetiform (multiple small coalescing ulcers).
- Oral lichen planus: T-cell mediated, Wickham striae, bilateral buccal involvement, saw-tooth rete ridges and a band-like lymphocytic infiltrate; low but real malignant potential.
- Pemphigus vulgaris: IgG against desmoglein 3, suprabasal acantholysis with 'tombstone' basal cells, positive Nikolsky sign, Tzanck smear shows acantholytic cells.
- Mucous membrane pemphigoid: linear IgG and C3 at the basement membrane, subepithelial split, gingival desquamation, scarring ocular lesions.
- Trigeminal neuralgia: paroxysmal lancinating pain in a division, triggered by touch; carbamazepine is first line and MRI excludes secondary causes.
- Radiographic signatures: ground glass in fibrous dysplasia, cotton-wool in Paget's disease, sunburst periosteal reaction in osteosarcoma, onion-skin in Ewing's sarcoma, soap-bubble in ameloblastoma or central giant cell lesion, honeycomb in intraosseous haemangioma.
Worked example
A 58-year-old tobacco chewer has a 3 cm ulcer on the lateral tongue present for seven weeks, indurated with everted margins and fixed to deeper tissue. Duration beyond three weeks, induration and fixation are red flags for malignancy, so incisional biopsy of the representative margin is mandatory rather than a therapeutic trial. A traumatic ulcer would be tender, non-indurated and resolve within two weeks after the cause is removed - the reasoning here is that persistence plus induration changes the diagnosis from reactive to neoplastic.
Traps
- Diagnosing pemphigus on clinical appearance alone: the split level (suprabasal versus subepithelial) is what separates it from pemphigoid.
- Describing leukoplakia or lichen planus as definitely premalignant rather than as having malignant potential.
- Ordering CBCT as a first-line survey when a panoramic radiograph answers the question; ALARA applies.
- Missing that a unilocular radiolucency at an apex means a non-vital pulp test first.